Roll up, roll up people, for the great Tool lottery. It's time to throw an Aenima, a Parabola, and a few Ticks and Leeches, among many other twisted and scary songs, into a pot to see what comes out.

Because if Adam Jones, Tool's guitarist and creator of their macabre and ghoulish artwork and videos, is to be believed, that's how the Los Angeles-based art metal quartet go about putting their set lists together these days.

"What we do is we write all the names of the songs on little balls, we put them in this big cage, we give it a spin, and whatever song comes out we play," he laughs.

Even though he may be pulling TimeOut's leg, the lottery system sure threw up a few surprises on the band's mini American tour early last year when they played Ticks and Leeches off 2001's Lateralus. They've rarely played the song live because of the demands it places on frontman Maynard James Keenan's voice, with his shrieks sounding as if his throat is being held out and shredded by a sandstorm.

Whether they play that song when they return to New Zealand for a show at Vector Arena on May 8, we'll have to wait and see. Though Kiwi Tool fans, among the most devout in the world if the band's almost 200,000 album sales here is anything to go by (per capita the band's biggest-selling market), will be hoping all the hits, like Stinkfist and Sober and a few surprises, pop out of that spinning lottery cage.

The band are not touring in support of a new album; there's an express request before this interview not to ask when their long-awaited follow-up to 2006's 10,000 Days will be out (more on that later) - and are here on the back of supporting Black Sabbath at Ozzfest in Japan.

The Vector show is the band's first solo headlining concert here since playing the North Shore Events Centre in 2001, and follows two headlining slots at the Big Day Out in 2007 (a punishing and majestic performance) and in 2011 (a muddled show with sound problems and a lack of cohesion hampering their set).

Still, Tool are a band apart and it's a strange and beautiful song like Ticks and Leeches, which writhes, rumbles and lashes out over eight mighty minutes, that sums up the unique mentality that goes into making their music.

And even though their output is limited - they've released just four albums in 23 years - it's almost forgivable, considering their records are more like elaborate sonic artworks than just a collection of songs.

"We just click," says Jones. "There are four different people with four different ways of doing things, four different types of music, and they come together independently and make something sound successful. It's exciting."

"The most challenging time we have is when we are together," adds Justin Chancellor, an affable Brit and brawny bass player, who is also on the phone from Los Angeles with Jones.

It's this volatile working relationship that injects Tool's music with an inherent menace and heaviness. "There's an honest individuality in there and it's really inspiring that we're still together and we're trying to take [music] further."

It's been 20 years since Tool's debut album, Undertow, came out and, with songs like Sober, they became one of the heaviest and weirdest bands in mainstream music.

The last time Chancellor talked to TimeOut in 2010, he said he feared their music might start to "suck" as they got older. He was half joking, and is keen to qualify his comments today.

"When it stops being fun, and when it stops being good, that's when we stop doing it. And that hasn't been the case at all. We're currently involved in the biggest project of our lives," he says, referring to the forthcoming album.

It's been almost seven years since 10,000 Days, which is by far the longest break between the band's albums. Admittedly, in that time, they have taken breaks from recording to tour, Keenan spends much of his time at his winery in Arizona, and they all have side projects on the go - most notably Keenan's Puscifer and A Perfect Circle and Chancellor's MT Void.

Still, as Jones says, Tool is their main focus, and since it has been a long time between records, the big question really has to be asked: Are they happy with the new album and how it's going?

Hey, it's not as if we asked when the new album was going to be out. But with that there is a "beep" and Tool are gone, without even as much as a goodbye.